Wind Uplift Mitigation with Pedestal Paver Systems
Any paver laid without adhesives or other mechanical fixing on a rooftop, balcony or other exposed area on a high-rise building, will be subject to the force of wind, with the risk in some cases of the pavers becoming airborne. Of course, this wind uplift risk can be mitigated to some extent by using extra large or very heavy paving slabs, but this naturally reduces product options, particularly in colors and styles of paving or decking.
Since porcelain pavers are typically lighter than concrete pavers, but nevertheless can now be supplied in sizes as large as 48” x 96” which weigh 300lb, there can be some concern about their use in locations subject to very high wind. To check the validity of this concern, Archatrak commissioned the Florida International University Wall of Wind facility to investigate the wind speed at which lift up and blow off of 3/4″ thick 24″ x 24″ porcelain pavers and 24″ x 24″ structural Ipe wood deck tiles would occur.
The tests indicated that blow off (any paver carried away by the wind away from its original location) could occur under the following conditions:
- Ipe wood tiles – 12” high parapet, 8” high pedestals – 100 mph
- Porcelain pavers – no parapet, 8” high pedestals – 90 mph
- Porcelain pavers – 12” high parapet, 8” high pedestals – 110 mph
Archatrak has since been working on methods to reduce the risk of wind uplift of porcelain pavers when installed on a pedestal system. We currently offer two solutions, either using 2cm or 3cm thick pavers.
Kerf Cut Corners with Hold Down Washer
This system uses our thicker T30 porcelain pavers where a small semi-circular kerf is cut in each corner of the paver to accept a custom-made steel hold-down washer. (We can suggest a suitable saw for cutting the kerf at the building site on request). This method offers the advantages of:
- using standard (unmodified) components
- a relatively simple installation procedure
- using no adhesives
- no waiting for adhesives to cure
- the ability to lift up any individual paver for under deck maintenance
- no visible fixing devices on the surface of the deck
The pavers are securely fixed to the pedestal head with a stainless steel screw inserted through the center of the washer which in turn screws into the tapped head of the pedestal. We use corrosion resistant steel pedestals for this application, firstly since they provide a much more rigid structure than plastic pedestals and secondly, they are totally non-combustible.
We conducted an uplift test using a 3 x 3 array of (nine) porcelain pavers all secured to the steel pedestals in this manner, but restrained around the perimeter of the test bed with hold-down battens. The center paver of the array was connected to a pull tester and an upward force applied. The test was stopped at 600lb force. No failure of any of the components occurred at this point. Further laboratory testing is proposed to verify these results and determine the maximum force at which failure would occur.
More extreme uplift prevention may be possible by adhering the base of the pedestal to the membrane with a compatible adhesive.
Pavers Bonded to ‘SpanSafe’ Steel Trays with Adhesive
Since 2cm thick porcelain pavers are not thick enough to safely cut a kerf in each corner, we developed a system using powder coated, galvanized steel trays to which the pavers are adhered at each corner.
These ‘SpanSafe’ trays are constructed with raised steel quadrants at each corner which permit a hold down washer to secure the tray (plus paver) to the pedestal head in the same manner as the solution using 3cm porcelain pavers.
The 2cm thick pavers are bonded to the ‘SpanSafe’ trays with beads of Chemlink M1 or 3M 550 adhesive applied at each of the four corners. A washer is fitted in the space between the tray and the paver and screwed down tightly to the pedestal head. The steel construction ensures the screw cannot pull out when subject to strong uplift forces as can occur with plastic pedestals.
An added advantage of this system is that it not only provides break through protection for the pavers but can be used where a totally non-combustible deck is needed.
As with our 3cm pavers solution, more extreme uplift prevention may be possible, if required, by adhering the base of the pedestal to the membrane with a compatible adhesive.